In this application, Dr. Choi proposes to study the mechanism of hepatic lipase action, particularly lipoprotein removal. Hepatic lipase enhances lipoprotein uptake by lipolysis and forming a bridge between apo B of the particle and proteoglycans (HSPG) of the cell surface. Initial studies show that nonenzymatic bridging likely mediates uptake of apo B-containing lipoproteins (LDL and chylomicron remnants). Published studies showed that lipoprotein lipase (LPL) interacts with apoB via protein-protein interactions. Biochemical and cellular experiments are proposed to elucidate interactions between HL, lipoproteins and HSPG.